How the other half lives

First appearances can be deceptive. For a start, the rough track leading to Hammerwood Park, near East Grinstead, is decidedly inauspicious. The dirt road is pitted with potholes and gradually snakes downwards past rambling houses with neatly manicured lawns, a farm, a pond, a cricket pitch and then dense foliage, before twisting right to reveal what must be one of the country's most peculiar country piles.

Built in 1792 as a hunting-lodge, Hammerwood Park is a visual conundrum with optical illusions craftily designed to make the house look bigger and more imposing. It's one of only two houses in the UK designed by the young Benjamin Latrobe, who went on to the Capitol building in Washington DC and the porticoes of the White House. And its subsequent history is equally colourful, with numerous past owners including Led Zeppelin and a property developer who, in the Sixties, knocked the 50-room house into 11 flats.

Present owners are the Pinnegars, whose son David bought the crumbling pile in 1982 at the tender age of 21 with a family inheritance - his grandfather had made a small fortune out of putting rubber on table-tennis bats. Currently occupied by David, his wife, Anne-Noelle, their three small children and his parents, Eileen and John, Hammerwood Park is a living historical drama. No, not the guided tour in period costume variety which is increasingly popular in theme-park Britain. Nor the dry and dusty veneration of ancient relics favoured by purists. Witness, instead, the gripping contest of man versus every variety of rot, dilapidation and lack of funds.

"It immediately grabbed me," David says, attempting to explain his seemingly mad decision to purchase the place. A mere snip at pounds 140,000, Hammerwood then comprised little more than a crumbling shell set in 30 acres. It was an estate agent's nightmare - running water in most of the house, one-third of an acre of dry rot and 14 holes in the roof. "The advertisement said `in need of modernisation' - which was just what it didn't need. We were looking for a large country house to open to the public. We bought it to restore it, in the knowledge that it might otherwise suffer concrete floors and modern conversion."

The family has spent the past 15 years restoring the building, with much of the work done by self-employed craftsmen and volunteers. False walls were dutifully knocked down and covered ceilings were revealed. The philosophy throughout has been repair rather than replacement. Some of the results so far may seem a little threadbare - cracked windows are hung with broken shutters, peeling wallpaper prompts memories of the film Barton Fink and the nettle-filled garden is a work in progress - but, as David enthusiastically points out, "Hammerwood Park is not intended to be a house preserved in aspic."

"Guided tours by the family make a most interesting afternoon," the photocopied flier promises, with some understatement. Family members conduct visitors on a colourful tour of the building and its grounds, ending in tea with a fine collection of fresh cakes and home-baked scones, served beneath a replica of the Parthenon frieze in the Elgin Room, a former coach-house- turned-kitchen and a one-time badminton court.

Visitors are encouraged to understand the logic behind the house's unusual architecture. Unlike many country homes of that period, Hammerwood has no follies - the building is, in fact, itself a folly, David reveals. The house was built with pieces of stone declining upwards. Doric columns front Greek temple structures to the rear of the left and right wings. Each has been left plain, and designed to taper upwards to make the house appear bigger to approaching visitors.

Inside, you can tour many of the rooms - most of which are now midway through restoration, although telling gaps remain. "It's a question of priority," David explains. "Do we spend a couple of thousand pounds on replacing mirrored panels either side of the fireplace in the drawing- room, or on repairs to the roof and guttering?" A particularly pressing concern is the library, where shelves are caving downwards: evidence of rotting floor plates. And don't miss the dining-room, which has been left in an artful state of disrepair as a cautionary tale, complete with mould and shredded wallpaper.

Tours vary depending on day, group make-up and, of course, the members of the Pinnegar family on duty, although all are consummate storytellers. David, a physicist turned amateur classicist, is passionate about Hammerwood Park's Greek origins. His tour is an electric mix of ancient mythology and scattered references to the perils of drugs, Bosnia and global warming. Eileen offers a greater perspective on the families who have lived there: from the original owner, John Sperling to Oswald Augustus Smith, whose sister, Frances, was grandmother of the Queen Mother. And Led Zeppelin, of course. The band's grand scheme was to create a music complex, including studios and apartments for band members and their families. Their neglect left the building in ruin, the Pinnegars claim.

"It's a sacrifice - living in a house like this," Eileen confides. "But the reason we took this on was to prove that a family could take something at rock bottom and make it work." Private ownership restricts access to heritage grants and lottery funding. So, each family member has various businesses and schemes to plough further funds into its renovation, she adds. Hammerwood also regularly plays host to school parties studying the Greeks and operates a calendar of music and poetry events.

Hammerwood Park is in Sussex, just off the A264 between East Grinstead and Tunbridge Wells. Alternatively, you can reach it by train and take a taxi from East Grinstead station for pounds 6. The house is open to the public until the end of September on Saturdays and Wednesdays. Guided tours start at 2.10pm. Bed and breakfast accommodation is also available. For more information call: 01342 850594.